Can you explain clearly what you mean? The word "relativity" on its own has no specific meaning, just as the shape of Sheffield has no connection to whether Leeds can be seen.
Yes, it's quite simple, the view of an object seen by an observer, and their perspective, is relative to what they see in their event horizon! If two people were stood in the same place upon the earth, whether the earth is flat or a globe has no bearing upon what they both can see (considering that they have the same quality of eyesight)! However, if the two people concerned were stood on different parts of the earth, let's say in Sheffield or Leeds, the view of each in respect of the same object would depend upon whether person (a) was standing on a flat earth, and person (b) was standing on a globes earth (and vice versa)!Alternatively, both (a) and (b) might be considered to be standing on a flat earth, or as the case may be, both deemed to be standing on a globed earth!
In all examples, and all things being equal, the view of person (a), and / or, (b) would be relative to their location and position upon the earth!
The sun or the moon would not look any bigger or smaller if viewed at the same (fact) time by person (a) or (b), because it's relative to the fact that let's say the person at (a) in the centre of Sheffield, the exact position of the sun and the moon in altitude and latitude can never be reconciled with one another, theycan never be in the exact same position in the sky as viewed by person (b) in the centre of Leeds (at let's say some 35 miles away) because of 'time'. If it were possible to measure the radius and the circumference of the sun and the moon at 4.25pm on a given date by an observer in the centre of Sheffield, and at that precise moment in time by an oversee Dr in the centre of Leeds, there like obviously be either an increase in radias and circumference of both by a value equal to 35 miles in distance between both locations! The further observers are from one another at a specific time, the measurements would be lesser (if closer than 35 miles) or greater (if !interested than 35 miles distant)!...
